Frame

A frame is the PDU of layer2 datalink layer.
Frame consists of a header called Preamble just to represent its a frame.
Source MAC
Destination MAC
Data Length
Data
FCS - Frame Check Sequence. A value created by CRC (Cyclic Redundancy Check ) Algorithm

CRC is run on both Source and destination Layer 2.
If the FCS values are same in both, then the frame is accepted by the destination.
If not same it means it has errors and it it is rejected.
SOurce will heve to retransmit the frame again.